The present invention generally relates to parking brakes and more particularly relates to an electric parking brake system for a vehicle with an electronic control device controlling a wheel brake device and an operating element for actuating the electric parking brake system.
An electric parking brake system of the general type shown herein has already been disclosed in DE 41 29 919 A1. This publication describes a parking brake in the form of a power-brake system, in which the brake is actuated by an electric motor, with an electronic controller being electrically connected to sensors detecting the operating state of the vehicle. The electronic controller controls the brake-applying and releasing operations of the wheel brakes subject to signals coming from a brake-applying device and/or the sensors.
It has to be mentioned, that the provisions of ECE R 13.09 5.2.1.26.2 which apply to permits as of Feb. 22, 1997, require that electric parking brake systems (EPB) with an electric transmission device must be operable from the driver""s seat in case of an electric error, thus achieving a predefined locking effect. This locking effect relates to the static test on an inclined plane with a gradient of 18%. In the vehicle classes M1 and N1 resulting from the above-mentioned provisions, the effect of the transmission brake may also be used. Furthermore the EPB complying with the provisions mentioned above has to be released by devices carried in the vehicle.
It is the object of the present invention to avoid the disadvantages of the prior art and to create an electric parking brake system with expanded functionality, higher safety and improved comfort. In particular, the present invention shall provide a parking brake system enabling a controlled power braking, especially during travel, with high dynamics and involving slip-control processes.
The object according to the present invention is achieved in that an actuation of the operating element alternatively applies and releases the electric parking brake according to the driver""s request, if the vehicle is in a resting position.
According to one preferred embodiment of this invention, the actuation of the operating element applies the electric parking brake as long as said element is actuated, if the vehicle is travelling. Thus, a controlled braking can be executed in consideration of the current driving situation.
For reasons of safety, it is desirable that the electric parking brake according to the invention is provided with at least one sensor detecting the blocking of a wheel and consequently feeding a signal to the electric control unit. In order to avoid an uncontrolled driving condition, the electric control unit releases a brake application on the wheel as a reaction to the signal of at least one sensor.
An improvement of the present invention includes a parking operative mode of the parking brake system according to the present invention, in which, for reasons of comfort, the control unit automatically locks the electric parking brake system if the vehicle is parked.
A comfortable and safe further development of the present invention includes a first starting operative mode of the electric parking brake system according to the present invention, in which the electric control unit automatically releases the electric parking brake when starting the parked vehicle.
According to another development of the present invention, a second starting operative mode of the electric parking brake system according to the present invention is foreseen in which the electric control unit applies the parking brake system before starting the vehicle, if an operating element is actuated, releasing the brake during the starting process by means of suitable dynamics.
Advantageously, a third starting operative mode is foreseen, in which the electric control unit applies the electric parking brake system independently before starting the vehicle releasing it during the starting process. Thus it is avoided that the vehicle rolls away against the starting direction, wherein the desired starting direction can be determined e.g. by the selection of the speed (Hillholder).
Preferably, the electric parking brake includes at least one sensor detecting the angle of inclination of the vehicle and thus delivering a signal to the electronic control unit. In such a way the parking brake system can cause or support a braking process on the basis of an inclination without the driver having to initiate a separate braking process.
Just when parking in the vehicle, the driver has to execute a lot of activities. Therefore one way of parking in, in which the electronic control unit automatically actuates the electric parking brake system during the parking-in process, results in a particularly safe and comfortable operation of the parking brake system according to the present invention.
Advantageously, the parking brake system according to the present invention includes at least one distance sensor determining the distance between the vehicle and an obstacle, especially another vehicle, and delivering a signal to the electric control unit as a reaction to this. In such a way, the parking brake system according to the present invention can avoid a collision with the obstacle, especially when the vehicle is parked in.